In general, a scroll compressor includes a fixed scroll which has a spiral scroll wrap and maintains its fixed state regardless of rotation of a drive shaft, and a orbit scroll which also has a spiral scroll wrap and orbits during rotation of the drive shaft. In such a scroll compressor, the orbiting scroll orbits with respect to the fixed scroll with coolant being suctioned into a compressor chamber formed between the fixed scroll and the orbiting scroll, so as to compress the coolant.
An example of such a scroll compressor is disclosed in Korean Patent Laid-Open No. 2000-0041250 which will be briefly described with reference to FIG. 1.
As illustrated in FIG. 1, the conventional scroll compressor includes a compression mechanism for compressing coolant and a transmission mechanism for providing a driving force to the compression mechanism through a main shaft 3.
The transmission mechanism includes a stator 1 and a rotor 2, and the main shaft 3 is press-fitted into the rotor 2 to rotate in conjunction with the rotor 2.
The compression mechanism includes a fixed scroll 4 and a orbiting scroll 5. The coolant introduced through a suction pipe 6 is suctioned into compression chambers formed by the involuted wraps of the fixed scroll 4 and the orbiting scroll 5. When the main shaft 3 rotates, an Oldham ring 10 positioned on an upper frame 8 and a sliding bush 9 is connected to the orbiting scroll 5 through a unidirectional key groove so as to convert the rotation of the main shaft 3 to the orbit of the orbiting scroll 5.
Accordingly, the coolant introduced between the fixed scroll 4 and the orbiting scroll 5 gathers the two semicircular compression chambers formed by the two scroll wraps toward the centers of the scrolls to perform a compression operation.
As a result, the centrally gathered compression coolant is opened at a discharge port 11 on the rear surface of the fixed scroll 4, and the compressed coolant passes through the housing and is sent to a refrigerating/air conditioning cycle through a discharge pipe 12.
Meanwhile, it is necessary to supply lubricant frequently in order to minimize wear of the transmission mechanism and the compression mechanism. For this purpose, an oil pump 14 communicated with the main shaft 3 is provided below a lower frame 101.
The oil pump 14 is operated by the pressure difference in the compressor. That is, as the coolant of high temperature and high pressure discharged through the discharge port 11 flows from the left side to the right side, a pressure difference occurs between the suction side and the discharge side to operate the oil pump 14.
When the oil pump 14 is operated, the oil is supplied to the compression mechanism and the transmission mechanism through holes 3a formed within the main shaft 3 or grooves formed around the main shaft 3. The operation of the oil lubricates the mechanisms.
Here, the surface of the oil rises inclinedly toward the oil pump 14 due to the pressure difference during the supply of the coolant, and the oil which has performed the lubricating operation using the pressure difference flows toward the oil pump 14. Then, the oil is mixed with the coolant of high temperature and high pressure.
That is, when the oil which has performed the lubricating operation exits a coolant passage 102 formed in the lower frame 101, it is mixed with the coolant of high temperature and high pressure and collides with an oil separating plate 103 formed on the discharge side of the coolant passage 102.
In the process, the oil is separated from the coolant and is bent toward the lower side of a shell 15 by an inertial force to gather again, and the coolant of high temperature and high pressure exits the coolant passage 102 and then is discharged to the refrigerating/air conditioning cycle through the discharge pipe 12.
However, in the conventional scroll compressor, the holes 3a lengthwisely formed in the drive shaft functions only as a supply passage of oil but fails to function as a discharge passage.
Furthermore, although the conventional scroll compressor discloses a structure for separating oil from suctioned coolant, oil is separated regardless of the rotational speed of the drive shaft. Thus, oil cannot be sufficiently separated, resulting in decrease in the efficiency of the compressor. That is, since the oil separator is fixed even when the drive shaft of the compressor rotates at a high RPM due to a high thermal load, oil cannot be separated at a high efficiency.